1. Field of the Invention
The present invention relates to a projector type vehicle headlamp and more particularly to a vehicle headlamp with a movable shade.
2. Related Art
One type of projector type vehicle headlamp is provided with a projection lens disposed on an optical axis which extends in the longitudinal direction of the vehicle and a light source disposed further rearward than a rear focal point of the projection lens. Light from the light source is designed to be reflected to approach the optical axis by a reflector. When low beam light distribution pattern is formed by the projector type vehicle headlamp, part of reflected light from the reflector is intercepted by a shade which is disposed in such a manner that an upper end edge of the shade is located close to the optical axis in the vicinity of the rear focal point of the projection lens, so that a predetermined cut-off line is formed at an upper end portion of a low beam light distribution pattern.
Disclosed in JP-A-2002-056708 is a projector type vehicle headlamp which has, as the shade, a movable shade that moves between a first shape position where an upper end edge of the movable shade is located close to the optical axis in the vicinity of the rear focal point and a second shade position where the position of the upper end edge is located below the position thereof resulting when the movable shade is located at the first shade position.
Disclosed in JP-A-2002-042516 is a projector type vehicle headlamp with the aforesaid shade in which there is provided a light driving device for moving the light source between a first light source position which is located close to the optical axis and a second light source position which is located to the left or right of or below the first light source position.
In the vehicle headlamp described in JP-A-2002-056708, since a high beam light distribution pattern can be formed by moving the movable shade to the second shade position, the single lamp can be used to form both the low bean and high beam light distribution patterns.
In the vehicle headlamp described in JP-A-2002-042516, however, since the low beam light distribution pattern and the high beam light distribution pattern are formed by reflected light from the same reflecting area of the reflector, there is caused a problem that in the event that the reflecting area is formed into a reflecting surface shape which is suitable for the low beam light distribution pattern, a light distribution pattern which is suitable for the high beam light distribution pattern cannot always be obtained, whereas in the event that the reflecting area is formed into a reflecting surface shape which is suitable for the high beam light distribution pattern, a light distribution pattern which is suitable for the low beam light distribution pattern cannot always be obtained.
On the other hand, in the event that a lamp configuration with a movable light source such as described in JP-A-2002-042516, the luminous intensity distribution of the high beam light distribution pattern can be changed by moving the light source.
In the vehicle headlamp described in JP-A-2002-042516, however, since the shade is of a stationary type, there is caused a problem that a high beam light distribution pattern cannot be obtained. In addition, as is described in JP-A-2002-042516, there is caused another problem that the luminous intensity distribution of the low beam light distribution pattern can be changed but the degree of gathering light cannot be changed only by moving the light source in a direction which intersects with the optical axis at right angles.
These problems are problems that will be occurring not only when the low beam light distribution pattern is switched over to the high beam light distribution pattern or vice versa but also when the low beam light distribution pattern is switched over to an intermediate light distribution pattern (which is a light distribution pattern positioned at a middle between the low beam light distribution and the high beam light distribution) or vice versa.